[LeetCode]题解（python）：047-Permutations II

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题目来源

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https://leetcode.com/problems/permutations-ii/

Given a collection of numbers that might contain duplicates, return all possible unique permutations.

For example,
[1,1,2] have the following unique permutations:
[1,1,2], [1,2,1], and [2,1,1].

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题意分析
Input:list

Output:permutations

Conditions:跟上题类似，但是会有重复的元素

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题目思路

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直接用上题的做法，首先先排序，然后再遍历的时候用一个pre记录先前位置，如果当前位置与pre相同则跳过

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AC代码（Python）

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 class Solution(object):
     def permuteUnique(self, nums):
         """
         :type nums: List[int]
         :rtype: List[List[int]]
         """
         nums.sort()
         if len(nums) == 1:
             return [nums]
         res = []
         pre = None
         for i in range(len(nums)):
             if nums[i] == pre:
                 continue
             pre = nums[i]
             for j in self.permuteUnique(nums[:i] + nums[i+1:]):
                 res.append([nums[i]] + j)
         return res